Well, I'm not sure I'd take a whole lot of taper out, maybe .007" max at shoulder, and then 5 more degrees in the shoulder, it looks to me like you should expect around 2 more grains of room.
Whether that's worth a rechamber and new dies is up to you.
You might see some improvement with the light and mid-weight bullets.

Not even sure this cartridge even warrants that...
Kinda like the .308 Imp.. no real gain..
I heard that unless you gain 8% or better it just isn't worth it...

Man this cartridge is so efficient now and has such good accuracy potential .. I'm wondering what you see that I don't outta this thing??? Not that I am a no it all about this cartridge but just don't see what you do I guess...